Refrigeration systems are known for use with laboratory refrigerators and freezers of the type known as “high performance refrigerators” (the “high performance” label typically depending on specific limitations of peak temperature variation allowed within the refrigerator), which are used to cool their interior storage spaces to relative low temperatures such as about +4° C., −30° C. or lower, for example. These high performance refrigerators are used to store blood and/or plasma, in one example. It is typical in such refrigerators to have temperature sensor(s) which measure the air temperature within a cooled cabinet such that the temperature of products stored in the cabinet can be maintained at a desired level. When such products in the cabinet include blood or medicines, certain international or domestic standards may apply for how the temperature of such products needs to be regulated. Depending on how strict these standards can be, reliance solely on air temperatures when controlling the refrigeration systems may not be preferred to comply with the standards for cold storage of products like blood and medicines. For example, if a small temperature variation in the air temperature from a set point were only transitory and did not substantially affect the temperature of the products, a “false positive” activation of the refrigeration system may be caused when such an activation was not actually necessary, in these embodiments which only rely on air temperatures.
As a result, sensor mounting containers have been developed for use with these refrigerators and freezers containing temperature-sensitive products, with these sensor mounting containers including a ballast liquid, such as water, that a temperature sensor is inserted into rather than being directly exposed to the refrigerated air within the cooled cabinet. One example of such a conventional sensor mounting container is the sensor probe bottle included with laboratory refrigerators and freezers manufactured and distributed by the Applicant of the present invention (Thermo Fisher Scientific, of Asheville, N.C.). The sensor probe bottle is a container having a threaded neck and opening at the top end thereof, with the container being configured to hold a quantity of ballast liquid such as a solution of water and propylene glycol. The sensor probe bottle is mounted to a sidewall of the cooled cabinet, such as in a bracket secured to the sidewall, with a solid cap secured on the threaded neck to close the opening thereof. Another cap with a hole cut through the middle is provided to the customer, with one or more temperature sensors extending through the hole. In use, this cap is installed on the sensor probe bottle such that the temperature sensor(s) are inserted into the ballast liquid during use. These temperature sensors may be connected to display/alarm devices of the refrigerator or freezer, and/or also connected to the refrigeration system controlling the temperature within the cabinet. By placing the temperature sensor(s) in contact with ballast liquid instead of in direct contact with refrigerated air in the cooled cabinet, a better approximation of temperature of the products stored in the cabinet can be provided to the elements connected to the temperature sensor(s), e.g., the water/glycol solution can approximate products like blood and certain medicines which may be stored in the refrigerator or freezer.
However, the sensor probe bottle requires the use of temperature sensors which can operate while submersed in liquid, and such temperature sensors tend to be more expensive and complex than alternative sensors and probes. This additional expense comes from the need for protective equipment and heat conductive mediums that must be added to temperature sensors to make them submersible. Moreover, the opening in the bottle and the hole in the cap receiving the temperature sensor(s) provides a potential source of spillage or leakage of the ballast liquid when sensors are being positioned or replaced by a customer. While such spillage can be avoided when using the sensor probe bottle, the risk cannot be completely eliminated using the caps of the current design.
Other examples of prior sensor mounting containers are shown in U.S. Pat. No. 2,741,099 to Beane and U.S. Pat. No. 6,018,956 to Sakata et al. The containers shown in these documents fail to cure some of the drawbacks for sensor bottles and containers designed to position a temperature sensor in a ballast liquid. Furthermore, such container designs typically require specific positioning within a cooled cabinet at positions that negatively impact the total storage capacity within the cabinet.
There is a need, therefore, for further improvements in sensor mounting containers and the laboratory refrigerators and freezers using such sensor mounting containers for monitoring temperature of products stored in the laboratory refrigerators and freezers, which address these and other deficiencies of known designs.